Evaluation of Bi-Functional Electrochemical Catalytic Activity of Co3O4-CoFe2O4 Composite Spinel Oxide

Abstract

Oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are important for developing energy systems such as fuel cells and metal–air batteries. Precious metal catalysts, such as Pt and IrO2, have been considered electrochemical catalysts because of their excellent activity for the ORR and OER. However, their disadvantages, such as low durability for long-term operation and high price, necessitate the development of alternative electrochemical catalysts. Transition metal oxides with excellent electrical conductivity, high efficiency, and stability have been considered alternative electrochemical catalysts owing to their ORR and OER activities, which are similar to those of precious metal catalysts. Therefore, in this study, composite catalyst materials comprising Co3O4 and CoFe2O4 spinel oxides were synthesized via hydrothermal synthesis. The synthesized composite oxides exhibit bi-functional electrochemical catalytic activity for ORR and OER owing to the large active surface area and increased number of oxygen vacancies via the nanostrain in Co3O4 nanoparticles.

Influence of Calcination Temperature on Electrochemical Properties of Perovskite Oxide Nanofiber Catalysts

“…Pt/C exhibited a high activity and current density of −4.19 mA•cm −2 at −0.8 V and a limited current density of −4 mA•cm −2 at −0.25 V. The current density, which is affected by the geometric surface of the electrode, is related to the specific surface area. A higher specific surface area provides more active sites for the ORR, resulting in higher current densities [47,51]. As proven by many studies, SSC800, SSC700, SSC900, and SSC1000 were confirmed to exhibit high current density values in the order of specific surface area values.…”

Atomic Structure of Mn-Doped CoFe2O4 Nanoparticles for Metal–Air Battery Applications

“…As we already pointed out, the key problem is the poor electronic conductivity of cobalt ferrite electrodes [1,2], which limits their electrocatalytic performance. The DFT calculations [5] show that the introduction of Mn ions can improve the conductivity of cobalt ferrite.…”

“…Oxygen reduction (ORR) and oxygen evolution (OER) reactions are the key anchors underlying the electrocatalysis processes in energy systems such as metal-air batteries and fuel cells [1,2]. ORR and OER are sluggish electrochemical reactions that require a large quantity of precious metals as catalysts for enhancing activity and durability.…”

“…In fact, compared to the ORR, the OER is more challenging due to the extremely oxidative conditions at high potentials, where most of the currently studied carbon-based catalysts degrade due to rapid oxidation of carbon. Given the intrinsic stability of metal-based transition metal oxides, such as cobalt ferrite (CoFe 2 O 4 ), ORR and OER oxide catalysts could replace the carbon-based catalysts for reversible electrochemical technologies [1,2]. Cobalt ferrite is known to adopt the inverse spinel structure, where half of Fe 3+ ions are located at the tetrahedral sites (A-sites), while the octahedral sites (B-sites) host the remaining Fe 3+ and Co 2+ ions [5], some deviations from this ideal structure notwithstanding [6].…”

Atomistic Modeling of Spinel Oxide Particle Shapes and Reshaping under OER Conditions

“…This should open the way to cross-validation between theory and experiment, which should lead to a deeper understanding and then, eventually, to the rational design of much-needed more efficient and sustainable optimized catalysts in both oxidation and OER catalysis. In perspective, it will also be very interesting to further extend our approach by including defects such as oxygen vacancies in the surface energetics [53] or more complex composite architectures [54,55].…”